RAS: Introduce a FRU memory poison manager

Memory errors are an expected occurrence on systems with high memory
density. Generally, errors within a small number of unique physical
locations are acceptable, based on manufacturer and/or admin policy.
During run time, memory with errors may be retired so it is no longer
used by the system. This is done in mm through page poisoning, and the
effect will remain until the system is restarted.

If a memory location is consistently faulty, then the same run time
error handling may occur in the next reboot cycle, leading to
terminating jobs due to that already known bad memory. This could be
prevented if information from the previous boot was not lost.

Some add-in cards with driver-managed memory have on-board persistent
storage. Their driver saves memory error information to the persistent
storage during run time. The information is then restored after reset,
and known bad memory will be retired before the hardware is used.
A running log of bad memory locations is kept across multiple resets.

A similar solution is desirable for CPUs. However, this solution should
leverage industry-standard components as much as possible, rather than
a bespoke platform driver.

Two components are needed: a record format and a persistent storage
interface.

Implement a new module to manage the record formats on persistent
storage. Use the requirements for an AMD MI300-based system to start.
Vendor- and platform-specific details can be abstracted later as needed.

  [ bp: Massage commit message and code, squash 30-ish more fixes from
    Yazen and me. ]

Signed-off-by: Yazen Ghannam <[email protected]>
Co-developed-by: <[email protected]>
Signed-off-by: <[email protected]>
Co-developed-by: <[email protected]>
Signed-off-by: <[email protected]>
Tested-by: <[email protected]>
Signed-off-by: Borislav Petkov (AMD) <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: yghannam

MAINTAINERS

@@ -18363,6 +18363,12 @@ F:	drivers/ras/
 F:	include/linux/ras.h
 F:	include/ras/ras_event.h
 
+RAS FRU MEMORY POISON MANAGER (FMPM)
+M:	Yazen Ghannam <[email protected]>
+L:	[email protected]
+S:	Maintained
+F:	drivers/ras/amd/fmpm.c
+
 RC-CORE / LIRC FRAMEWORK
 M:	Sean Young <[email protected]>
 L:	[email protected]

drivers/ras/Kconfig

@@ -34,4 +34,16 @@ if RAS
 source "arch/x86/ras/Kconfig"
 source "drivers/ras/amd/atl/Kconfig"
 
+config RAS_FMPM
+	tristate "FRU Memory Poison Manager"
+	default m
+	depends on AMD_ATL && ACPI_APEI
+	help
+	  Support saving and restoring memory error information across reboot
+	  using ACPI ERST as persistent storage. Error information is saved with
+	  the UEFI CPER "FRU Memory Poison" section format.
+
+	  Memory will be retired during boot time and run time depending on
+	  platform-specific policies.
+
 endif

drivers/ras/Makefile

@@ -3,4 +3,5 @@ obj-$(CONFIG_RAS)	+= ras.o
 obj-$(CONFIG_DEBUG_FS)	+= debugfs.o
 obj-$(CONFIG_RAS_CEC)	+= cec.o
 
+obj-$(CONFIG_RAS_FMPM)	+= amd/fmpm.o
 obj-y			+= amd/atl/